Fig. 3

Expression of the bgaB reporter gene from inducible and inducer-free plasmids in B. subtilis 1012. Synthesis of the reporter protein BgaB expressed from the three different vectors pHT01-bgaB (Pgrac01-bgaB, inducible), pHCMC02-bgaB (PlepA-bgaB, inducer-free) [12] and pHT1655 (Pgrac01-bgaB, inducer-free) in the presence and absence of 1 mM IPTG. The empty vector pHT01 served as a negative control. The bacterial cells carrying these vectors were grown in LB medium at 37 °C to the mid-logarithmic growth phase. Then, the culture was split into four subcultures, where one was further incubated in the absence of IPTG (0 mM) and other three induced with 0.01, 0.1 and 1 mM IPTG. Samples were taken 2 h after addition of IPTG. a SDS-PAGE analysis of bgaB inducer-free expression in B. subtilis in the absence or presence of 1 mM IPTG and visualized by Coomassie brilliant blue staining. b The β-galactosidase activity was measured in all samples and expressed as MUG units (×10⁴)